The current proliferation of front wheel drive vehicles with liquid-cooled engines mounted transverse to the longitudinal axis of the vehicle has complicated traditional cooling fan drive arrangements wherein the engine is mounted parallel to the longitudinal axis. Vehicles with either longitudinally or transversely mounted engines preferably have the radiator positioned forwardly of the engine and in a plane transverse to the longitudinal axis since such positioning provides direct access for ambient air flow through the radiator, particularly ram air, and since space for the radiator is readily provided with such positioning.
In vehicles with longitudinally mounted engines, forwardly mounted radiators, and axial flow fans mounted therebetween, the axial flow fans are conveniently mounted on the front of the engines with the rotational axes of the fans positioned parallel to the engine crankshaft axes and the fans are readily driven by mechanical drives such as belts driven by pulleys mounted on forward projections of the engine crankshafts. Such drive arrangements are simple, reliable, relatively inexpensive, and last, but not least, relatively efficient. In vehicles with radiators mounted forward of the engines and parallel to the rotational axes of the engine crankshafts (as is the case with transverse engine vehicles), axial flow fans cannot be readily mounted on the engines with the rotational axes of the fans parallel to the crankshaft axes and cannot be readily driven by mechanical drive arrangements such as belts driven by pulleys mounted on projections of the engine crankshafts, since the necessary space for such arrangements is not available. Hence, vehicles with transversely mounted engines and radiators mounted forward of the engines and parallel to the axes of the engine crankshafts, for the most part, now use electric motors to drive the fans. The electric motors are in general more expense than mechanical drive arrangements and are believed to be less reliable. Further, since the electric motors are price sensitive per unit horsepower and are substantially less efficient than mechanical drives, some vehicle manufacturers have increased the size of the radiators to reduce motor size and have spent considerable time developing more efficient fans to further reduce motor size.
One prior art reference, U.S. Pat. No. 3,696,730 issued Oct. 10, 1972, schematically discloses a transverse engine vehicle with a forwardly mounted radiator and several embodiments of mechanically driven fans. One of the embodiments discloses a centrifugal fan with axial inlet and radial outlet mounted on one end of the engine. The other embodiments disclose axial flow fans transversely disposed with respect to one end of the engine and with the rotational axes of the fans either in line with the engine crankshaft axis or forward thereof. All of these embodiments require transverse offsetting of the radiators and/or the engines, transverse offsetting of the fans, bulky ducts for directing air to and from the fans, and tortuous flow paths for the air. Transverse offsetting of the radiators though possible even in relatively small cars is not desirable since it interferes with headlight and fender mounting unless the front of the vehicle is extended to provide additional room. Transverse offsetting of transversely mounted engines is undesirable since it upsets vehicle weight distribution and as a practical matter, there is insufficient transverse space for such offsetting in passenger vehicles with forwardly mounted transverse engines. Likewise, there is insufficient transverse space for transverse offsetting or positioning of the fans at one end of the engines. Further, the bulky or large ducts for directing the air to and from the fans would at best be difficult to install in the limited space available in such vehicles.
In addition, the cooling fan embodiments of the above mentioned patent do not provide means to vary the fan speed in accordance with engine cooling needs. In a present day vehicle with air-conditioning, a cooling fan having the pumping capacity to cool both the engine radiator and the air conditioner condenser has far more pumping capacity than is needed when the air conditioner is not in use or when the forward speed of the vehicle is great enough to provide cooling by ram air. Such excess fan capacity puts a substantial horsepower drain on already small engines and wastes energy.